BANGKOK  They may thrive on land and in water, but amphibians everywhere are in serious trouble, and up to one-third of species are threatened with extinction, a troubling new study said on Friday.

Scientists say this is an ominous sign for other creatures, including humans, as amphibians are widely regarded as biological "canaries in the coal mine," since their permeable skin is highly sensitive to changes in the environment. In short, they go first, and others follow.

The first comprehensive survey of a grouping that includes frogs, toads, and salamanders, the Global Amphibian Assessment says that at least nine species have become extinct since 1980. It says 113 more have not been reported in the wild in recent years and are believed to have vanished. The full details will be published in a few weeks in the respected journal Science.

"Amphibians are one of nature's best indicators of overall environmental health," Conservation International President Russell Mittermeier said in a statement from the World Conservation Union (IUCN), one of the world's top environment bodies.

"Their catastrophic decline serves as a warning that we are in a period of significant environmental degradation," he said in the statement that coincided with the final day of a two-week meeting of signatories to the Convention on International Trade in Endangered Species (CITES) in Bangkok.

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After birds and mammals, amphibians are only the third broad group of animals to be surveyed on such a global scale. More than 500 scientists from more than 60 countries contributed to the report.

The three-year study analyzed the distribution and conservation status of all 5,743 known amphibian species. Scientists from Conservation International and the IUCN collaborated on the study.

Hopping to Extinction

In the Americas, the Caribbean, and Australia, a highly infectious fungal disease called chytridiomycosis is taking a big toll on amphibians.

Air and water pollution, habitat destruction, climate change, the introduction of invasive species, and consumer demand are the biggest global threats.

About one-third  at least 1,856 amphibian species or 32 percent of them all  are threatened with extinction. By comparison, only 12 percent of bird and 23 percent of mammal species are endangered.

The study also found that the populations of 43 percent of all amphibian species are in decline, while fewer than 1 percent are rising. It found that 27 percent are stable and the rest are not known.

"The fact that one-third of amphibians are in precipitous decline tells us that we are rapidly moving toward a potentially epidemic number of extinctions," said Achim Steiner, director-general of the IUCN.

The study adds to an alarming body of evidence that the planet is facing a sixth wave of "mass extinctions," the first since the dinosaurs perished 65 million years ago. But this round of die-offs is human-made.

The report also highlights the link between poverty and environmental degradation. Dirt-poor and conflict-ridden Haiti has the highest percentage of threatened amphibians, with 92 percent of its species facing extinction.